Create flag to print final mlir module

[causten]

Add a parameter for migraphx-driver to print the mlir fusion graphs per model. MIGraphX today already has the ability to print MLIR code objects so this will be to identify the winning one since today; using an environment variable, it prints them all during the tuning phase. Do not print all, just the ones that will be run in the model. The driver should export each chosen fusion graph via in a well structured manner for rocmlir to import the file(s) (.mlir?).

rocmlir will compile them (ensuring that a single code object is generated), verify them, and benchmark them.

[pfultz2]

We already have a flag to print the mlir modules. Instead, we should have env variable to a path to dump each mlir program to an individual file. #3182 dumps them to mxrs, we just need to another variable to dump the mlir instead. Either way, #3182 needs to be merged in first.